The purpose of this multicenter, dose-ranging study is to compare two Fixed-Dose Combinations of aclidinium bromide and formoterol fumarate with placebo, aclidinium bromide and formoterol fumarate, all administered BID in patients with stable, moderate to severe COPD.

Every treatment period is 14-days long and there is a 7-days wash-out period in between them. The trial starts with a run in phase of 10 to 17-days duration and it ends up with a follow up contact 14-days after last treatment dose.

Inclusion Criteria:

1. Adult male or non-pregnant, non-lactating female aged between 40 and 80 years old, both inclusive.
2. Patient with a clinical diagnosis of stable moderate to severe COPD according to the GOLD classification
3. Current, or ex-cigarette smoker with a smoking history of at least 10 pack-years.
4. Patient whose FEV1 at the Screening Visit measured between 10-15 minutes post inhalation of 400 mcg of salbutamol is 30% FEV1 <80% of the predicted normal value (i.e., 100 x Post-salbutamol < FEV1/ Predicted FEV1 must be < 80% and ≥ 30%).
5. Patient whose FEV1/FVC at the Screening Visit measured between 10-15 minutes post inhalation of 400 mcg of salbutamol is < 70% (i.e., 100 x Post-salbutamol FEV1 /FVC < 70%).
6. Patient who is eligible and able to participate in the trial and who consent to do so in writing after the purpose and nature of the investigation have been explained.
7. Patient whose COPD symptoms and FEV1 values at the time of randomisation are stable compared to the Screening Visit, according to the investigator's medical judgment

Exclusion Criteria:

1. History or current diagnosis of asthma or exercise-induced bronchospasm.
2. Clinically significant respiratory conditions at the time of Inform Consent signature
3. Hospitalisation due to COPD exacerbation within the previous 3 months.
4. Signs of a COPD exacerbation or respiratory infection (including the upper respiratory tract) within the previous 6 weeks.
5. Patient who has a resting systolic blood pressure ≥ 200 mmHg, a resting diastolic blood pressure ≥ 120 mmHg or a resting heart rate ≥ 105 bpm at screening visit.
6. Clinically significant cardiovascular conditions
7. Presence of symptomatic prostatic hypertrophy and/or bladder neck obstruction.
8. Presence of narrow-angle glaucoma.
9. QTc [calculated according to Bazett's formulae (QTc=QT/RR1/2) above 470 milliseconds in the ECG performed at Screening Visit,
10. Patient who does not maintain regular day/night, waking/sleeping cycles](streamdown:incomplete-link)